However, in the real rather than the virtual world, there are as yet no human brains operating in artificial bodies. And although bionic people have been around for a long time, until recently their artificial parts have been primarily mechanical, not neural, and represent rela- tively small bodily changes. Replacements for missing limbs and cos- metic additions such as breast implants are immensely significant to the implantee, but they do not turn people into cyborgs—nor is any- one yet proposing to transplant a living brain into a metal body. Still, the latest chapter in the real history of artificial beings is a step toward this fusion; it is the formation of direct connections between living organic systems and nonliving ones at the neural and brain levels.

The key idea behind this synthesis draws on the electrical nature of the signals in the nerve network and the brain and envisages con- necting neural systems to electronic ones. Outcomes already begin- ning to be realized include an interface that allows a paralyzed person to manipulate a computer purely by mental control, without physical effort; hybrid neural-electronic chips, in which a living neuron and an electronic circuit mounted on the same piece of silicon communicate with each other; and the use of animal brains to control mobile bod- ies and robotic arms, as a step toward providing mentally controlled devices to the paralyzed.

These developments fall under new areas in neural research and clinical practice called neurorobotics or neuroprosthesis, but artificial additions to human bodies have a long history that—like the develop- ment of artificial beings themselves—reflects successive waves of tech- nology. Prostheses that use digital electronics owe their invention, in turn, to the development of implant surgery and to the scientific in- troduction of electricity into the body. But first came simpler physical prostheses without electronic components, made to meet the needs of those born handicapped, injured through accident, or wounded in war. Such prostheses fell into two categories: functional, to replace lost physical capability, and cosmetic, to rehabilitate damaged appearance.